New Concept Motor with Dual Rotors Driven by Harmonic AC

This paper describes two methods of driving a multi-motor system by one inverter set, which is intended for application to hybrid vehicles for improving fuel economy. With one method, a dual-rotor motor shares a single stator excited by one inverter, but the speed of the two rotors can be controlled independently. With the other method, two motors are connected in parallel by means of a special coil wiring technique that allows them to be controlled independently by one inverter. Simulations of the dual-rotor motor were performed with an equivalent electric circuit model to calculate the electric current, voltage, torque and speed. It was found that the magnetic reluctance balance among the stator teeth is an important variable for the high performance of this dual-rotor motor. The ability to drive two motors independently was then verified and demonstrated experimentally. An experiment was also conducted to verify the effect of harmonic electric current on reducing inverter loss. The loss reduction by harmonic current and the miniaturization by the dual-rotor motor aim at efficient-ization of a HEV system.